Duangrudee Chaysuwan

Geopolymer Development by Powders of Metakaolin and Wastes in Thailand

Geopolymer has been developed as an alternative material to Portland cement. Geopolymer is based on the polymerization of alkaline activation and oxide of silicon and aluminium. These oxides can be found in many pozzolanic materials such as metakaolin and the wastes from industries and agricultures in Thailand, e.g., fly ash, bagasse ash and rice husk ash. Pozzolanic materials were selected as source materials for making geopolymers into 4 different types. Sodium hydroxide concentration of 10 Molar (10MNaOH) and sodium silicate (Na2SiO3) solutions were used as alkaline activators by the mass ratio of Na2SiO3/NaOH at 1.5. The mixtures were cast in 25×25×25 mm. cubes. After casting, the geopolymers were cured at 80๐C for 24 hrs. in an oven and then at room temperature for 7 days. The pozzolanic materials effects, the Si/Al molar ratio and the Na/Al molar ratio were studied and characterized. An X-ray fluorescence (XRF) was chosen to determine the percentages of silica and alumina in order to verify the proper ratio of the fly ash, Rice husk ash, Bagasse ash and Metakaolin.The study also included the impact on mechanical and physical properties such as compressive strength, water absorption, density and porosity.

Metakaolin-Based Porous Geopolymer with Aluminium Powder

Porous concretes such as aerated and lightweight concretes are commonly used in construction fields. Lightweight construction materials are used to reduce either the weight or the budget of building structures. Porous concrete production is widely utilised aluminium (Al) powder to increase pores in concrete structures and giving information for porous geopolymer production. It was introduced by adding 0.05-1% Al-powder as the initiated materials of geopolymers, to react with water in those materials and promote hydrogen gas inside specimens. The research, therefore, focused on the synthesis of porous geopolymer by metakaolin as a pozzolan and mixed with alkali solution (8M NaOH and Na2SiO3) as well as Al-powder as a foaming agent. The highly porous geopolymers were produced with various Al-powders as 0%, 0.2%, 0.4%, 0.6% 0.8% and 1% by weight. After 7, 14 and 28 days age, the specimens were tested the mechanical properties, such as compressive and flexural strengths. The water absorption, apparent porosity and bulk density were analyzed at 28 days age. The synthesis of metakaolin-based porous geopolymers with Al-powder presented good results. It showed that Al-powder content affected to degree of porosity of geopolymers. Keywords: Metakaolin based geopolymer, Porous geopolymer, Aluminium powder, Foaming agent, Mechanical and physical properties

Properties of Geopolymer Paste from Fly Ash Blended with Metakaolin as Pervious Concrete

The purpose of this research was to study pervious geopolymer concrete with different amounts of lignite fly ash (F), metakaolin (M), sodium silicate (NS) and 8 mol/L sodium hydroxide (NH) solution. Constant NS/NH ratio of 0.5, three alkali liquid/pozzolan (L/P) ratios viz., 0.5, 0.6 and 0.7 and pozzolan to coarse aggregate ratio of 1:8 were used. The compressive strengths of 50×50×50 mm3 cube specimens were tested at the age of 28 days. In addition, compressive strengths of 100 mm in diameter and 200 mm in height cylindrical specimens were tested at the age of 7, 14, 21 and 28 days. The chemical compositions and microstructures of specimens were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM), respectively.The mixture with 50%F+50%M and L/P ratio of 0.7 was the best proportion for pervious geopolymer concrete according to the compressive strength, good permeability and microstructural images. The bond of Si-O-Al and Si-O-Si characterized by Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the developed geopolymeric structure.

Effect of Heat Treatment Time on Properties of Mica-Based Glass-Ceramics for Restorative Dental Materials

The objective of this research is to focus improving the properties of machinable mica-based glass-ceramics in order for restorative dental materials. The glass-ceramics derived from the SiO2- Al2O3-MgO-MgF2-SrCO3-CaCO3-CaF2-P2O5 system were produced by a two-stage heat treatment. It was elucidated that the optimum nucleation and the crystallization temperatures were at 643°C and 892°C. The various heat treatment times in the first stage were applied as 3, 6, 12, 24, 48 and 72 h, respectively, on the optimum nucleation temperature to produce mica-based glass-ceramics. XRD results showed that specimens of variety of nucleation time had similar crystalline structures such as calcium-mica, fluorapatite, stishovite, anorthite, strontiumapatite and forsterite phases. The microstructures of glass-ceramics were observed by SEM basically as interlocked plate-like and needle-like microstructures of mica and fluorapatite, respectively, in all specimens. Furthermore, different heat treatment times influenced on the revealed crystal size of the glass-ceramics; the longer heat treatment, the smaller crystals. The resultant glass-ceramics gave the results of biaxial flexural strength (178-224 MPa) and Vickers hardness (295-393 HV) increasing with the formation of the interconnected mica phases which contributed to improve the machinability. The values of the properties were comparable to those of human enamel and suitable for some restorative dental applications.

Nucleation, Crystallization and Characterization of Mica-Based Glass-Ceramics with Fluorapatite

The glass system of SiO2-Al2O3-MgO-MgF2-SrCO3-CaCO3-CaF2-P2O5 was used to prepare machinable glass-ceramics for restorative dental applications. The aim of this study was to apply various heat treatments to produce mica-based glass-ceramics. Differential Thermal Analysis (DTA) was used to determine the optimal heat treatment conditions for nucleation and growth of the crystalline phases in the quenched glass. It was found that the optimum nucleation temperatures for the first and the second crystallization temperatures (Tp1 and Tp2) were 642°C and 635°C, respectively, and the optimum nucleation times were between 2 and 4 hours. X-Ray Diffraction (XRD) showed the phases developed were anorthite, calcium-mica, fluorapatite, strontium apatite, forsterite, fluorite and stishovite phases. The microstructures of glass-ceramics were observed by Scanning electron microscope (SEM), found to exhibit plate-like mica crystals with high interlocking and randomly oriented with a higher soaking temperature and prolongation of the soaking time for crystallization.

Moisture Control Capacity of Geopolymer Composites: Correlation of the Bulk Composition–Pore Network with the Absorption–Desorption Behavior

Porous composites with the principal class of porosity in the range of those presented in the literature as ideal for the moisture control capacity of building environment are described. In the course of the design of the matrices, micrometric pores are introduced to give to the pore systems a bi- or multimodal characters with the aim of improving the phases percolation during the course of desorption and make the moisture accumulation–desorption behavior of the porous composites essentially function of weather and environment. The porous composites present size of pores in the range

Development of Geopolymer Mortar from Metakaolin Blended with Agricultural and Industrial Wastes

0.001{-}1\, \upmu \hbox {m}

Effect of Porosity and Pore Size on Microstructures and Mechanical Properties of Metakaolin Blended with Ca(OH)2 and PLA as Porous Geopolymers

0.001-1μm for the gel pores and peak centered at